Aspen stands:Aspen stands:Fuel or Fuelbreak Fuel or Fuelbreak at a Landscape at a Landscape

Scale?Scale?

IntroductionIntroduction

•Do aspen stands make good Do aspen stands make good strategic (landscape scale) strategic (landscape scale) fuelbreaks for community fuelbreaks for community protection and commercial forest protection and commercial forest protection?protection?

•Effectiveness varies with burning Effectiveness varies with burning conditions and fuel loads.conditions and fuel loads.

In spite of In spite of sophisticated sophisticated

fire fire management, management,

fire still fire still operates at a operates at a

landscape landscape scalescale

75 year Okanagan fire 75 year Okanagan fire history map shows:history map shows:

• ½ the area burned ½ the area burned at least onceat least once

• Significant areas re-Significant areas re-burnedburned

• 90% of lightning 90% of lightning fires suppressed at fires suppressed at <0.1 ha<0.1 ha

• Large fires in 1920s, Large fires in 1920s, 1930s, 1990s, 20031930s, 1990s, 2003

• No large fires in No large fires in Okanagan Mountain Okanagan Mountain ParkPark

Okanagan Okanagan Mountain Park Mountain Park Fire, 2003Fire, 2003

• Severe drought Severe drought and windand wind

• Entire 10,000 ha Entire 10,000 ha park burned in park burned in 25,000 ha fire25,000 ha fire

• East half of fire East half of fire burned before burned before (1920s, 1930s)(1920s, 1930s)

• No landscape-scale No landscape-scale fuelbreaksfuelbreaks

• Only 2000 ha of 1.66 M ha burned/year Only 2000 ha of 1.66 M ha burned/year (0.12%)(0.12%)

• Not enough fire to maintain fire-Not enough fire to maintain fire-dependant ecosystems in crown fire-dependant ecosystems in crown fire-resistant stateresistant state

• Solutions include community fuelbreaks, Solutions include community fuelbreaks, prescribed burning, home ignition zone prescribed burning, home ignition zone fuel reductionfuel reduction

South Okanagan fire historySouth Okanagan fire history

Limitations/constraints Limitations/constraints on fuel reductionon fuel reduction

• Most burned area Most burned area associated with associated with synoptic-scale weather synoptic-scale weather patternspatterns

• Fuelbreaks may fail in Fuelbreaks may fail in extreme burning extreme burning conditions of drought, conditions of drought, low RH, high windslow RH, high winds

• Prescribed burning is Prescribed burning is risky, requires skills and risky, requires skills and experience in short experience in short supply, and smoke is a supply, and smoke is a problemproblem

Limitations/constraints on fuel reductionLimitations/constraints on fuel reduction

•Prescribed fire effects Prescribed fire effects unlikely to override unlikely to override extreme weather, extreme weather, especially areas subject especially areas subject to wind and droughtto wind and drought

•Expensive to Expensive to reduce fuel loads at reduce fuel loads at landscape scalelandscape scale

Limitations/constraints on fuel reductionLimitations/constraints on fuel reduction

•Fuel reduction Fuel reduction measures are not measures are not one-time events, one-time events, their impacts are their impacts are short-termshort-term

Limitations/constraints on fuel reductionLimitations/constraints on fuel reduction

Chisholm Fire Study

Weather Conditions & Fuel Moisture

Weather Conditions• Three year moisture deficit, Slave Lake area• Dry spring followed light snow pack• Heavy fuels and forest floor drier than normal• Fine fuels dry, warm temp, low RH, windy• Conifer foliar moisture near its annual minimum• Greenup of grass and herbaceous vegetation

delayed by drought

• Previous area May record BUI=121 (1991), ISI=41, FWI=60

Chisholm Fire StudyFire Weather Observations and Peak Weather Indices

For May 28th 2001

Chisholm Base Stn. C1

Temperature RH W. Dir. W. Speed(°C) (%) (Degrees) (km/h)

Peak 1900 hr 23 34 180 49

FFMC DMC DCStd. Daily 91.7 101.0 388.0

Peak 1900 hr 92.8

ISI BUI FWIStd. Daily 55.0 122.0 98.0

Peak 1900 hr 74.4 116.0

Chisholm Fire, FBP Fuel Type Map

Weather Conditions & Fuel Moisture

Fuel Types• Boreal Spruce (C2) predominates (39%)• Cured standing grass (O-1b) significant

(35%) due to reburn in 1998 Mitsue and Chisholm burns

• Leafless aspen (D-1) significant (18%), generally has conifer understory

• Boreal mixedwood - leafless (M-1) (3%), generally has 25-50% conifer

• Mature pine (C-3) significant on benches along Athabasca River, minor overall (3.5%)

Special situations

• Grass fuels were 100% cured and standing, due to low snowpack and dry spring• Deciduous stands (0-1) had begun leaf-out, but grass and herbaceous vegetation in stands had not• Extensive 30 year old aspen stands from 1968 Vega Fire along west flank

Chisholm Fire Behavior and Effects in Aspen

•All overstory trees killed, all plots•Vigorous aspen suckers, all plots•Herb and shrub response vigorous, all plots•Grass sparse on CFS plots, significant on Vega plots

Chisholm Fire Behavior and Effects Chisholm Fire Behavior and Effects in Aspenin Aspen

•Fire intensity 10 times higher on Fire intensity 10 times higher on CFS plots, due to fire history, fuel CFS plots, due to fire history, fuel load and rate of spreadload and rate of spread•Highest intensity established for Highest intensity established for CFS plot = 228,000 kW/mCFS plot = 228,000 kW/m•Highest intensity established for Highest intensity established for Vega plot = 27,000 kW/mVega plot = 27,000 kW/m

Fuel loads and fuel consumptionFuel loads and fuel consumption

•Much higher fuel loads established Much higher fuel loads established on CFS plots due to falldown of on CFS plots due to falldown of natural mortality + 1972 and 1978 natural mortality + 1972 and 1978 fire-killed treesfire-killed trees•Downed-woody fuel loads much Downed-woody fuel loads much lower on Vega Fire plots due to lower on Vega Fire plots due to salvage logging after Vega Firesalvage logging after Vega Fire

•Drought conditions in 1968 and 2001 contributed to high consumption of downed-woody fuel and forest floor

CFS Plots (kg/m2)

Vega Fire Plots (kg/m2)

Forest floor consumption 1.5 0.9 - 3.7 Downed-woody consumption 6.1 0.5 Total Fuel consumption 7.6 1.4 - 4.3 Predicted TFC (FBP System) 1.3 1.3

CFS Plots Vega Fire Plots

Mineral soil exposure (average %) 30 0

Tree bole-scorch height (m) 3.6 0.5

•Higher than predicted aspen fuel Higher than predicted aspen fuel consumption if spring burning consumption if spring burning conditions severe and/or fuel loads conditions severe and/or fuel loads highhigh

•Under-estimation of potential Under-estimation of potential aspen fire behavior may result in aspen fire behavior may result in over-estimation of benefits of aspen over-estimation of benefits of aspen stands as fuelbreaksstands as fuelbreaks

Landscape fuel management Landscape fuel management interpretationsinterpretations

Large stands of aspen were Large stands of aspen were effective at stopping fire spread effective at stopping fire spread under severe spring burning under severe spring burning conditions when:conditions when:

•downed-woody fuel loads were downed-woody fuel loads were light, and light, and •cured grass is not a factorcured grass is not a factor

Landscape fuel management Landscape fuel management interpretationsinterpretations

•Aspen Fuelbreaks should:Aspen Fuelbreaks should:

•Maximize canopy closure to Maximize canopy closure to exclude grass, andexclude grass, and

•Reduce downed-woody fuel Reduce downed-woody fuel loads to a single ground layerloads to a single ground layer

Landscape fuel management Landscape fuel management interpretationsinterpretations